The instant invention is directed to a process for the production of an aromatic isocyanate containing aromatically bound sulfochloride groups, comprising:(I) reacting(a) an isocyanate or carbamic acid chloride which contains at least one aromatically bound isocyanate group and/or at least one aromatically bound carbamic acid chloride group, successively or simultaneously at 0.degree. to 170.degree. C. with(b) a sulfonating agent and(c) an organic compound containing at least one aromatically bound trihalo methyl group and(II) removing hydrogen chloride from the reaction mixture at 20.degree. to 170.degree. C.